I have the SX500-LG, I tried that PSU in my SG08-Lite but quickly went back to my previous PSU (Antec NeoEco 520W) even if it's not as good. You can't use the SFX --> ATX adapter as the modular cables get in the way of a long GPU. Even without using the adapter (I fixed the PSU with double tape), the cables still push hard against the GPU and the PSU intake doesn't line up with the PSU fan so it isn't great.
From my experience, to get the best fit in the SG08 with a long GPU you need a non-modular 140mm deep ATX PSU. You'll be able to save money or get higher wattage PSU too
(the SX500-LG is quite expensive compared to standard ATX PSUs at equal wattage)
I also have the MSI GTX970 Gaming 4G in the SG08 and it barely fits due to height (and I can confirm you either need to remove the ODD bracket or cut it due to the GPU heatpipes). So if the GPU you're looking at is taller than MSI GTX970 Gaming (which is 140mm according to their website) there'll probably be issues.